Cm870 oil loss

[Nwttrucking]

Cummins reman.
Checked oil after turbo was replaced. Hauled 3 loads of rock and checked it again and it was a gallon low. Couple drops out of the breather tuber from sitting over night. Limited blow by. Couldn't see any smoke when it was loaded, but empty theres maybe slight haze of blackish smoke when flooring it for a sec, but pretty normal for just fuel being burnt. Turbo was dry all over just typical soot on the exhaust side. Fuel tank is clean, coolant is clean, air dryer clean. Curious if an oil ring got stuck or broke. Ran the truck to a shop for 45 mins and it didn't lose a drop of oil, so my guess is it only happens under load. Truck is doing a silent derate to 20psi max boost with no lights coming on, but I believe thats a seperate issue because the shop left a huge leak at a v band clamp on the egr, or possibly some sensor failing? A gallon in 3 hours I would think would have left some sort of wet residue coming out of the turbo, but it looks dry.